Traditional drug delivery methods, such as introducing plasma concentrations of drugs by injection, or inhalation and ingestion of drugs, can require repeated and relatively greater dosing, with problematic patient compliance. Chemotherapy, which applies these methods for cancer treatments, can adversely affect healthy cells thereby causing serious side effects. Compared with these methods, a controlled local release system provides the desired constant drug concentrations at the target specific areas of the body, lowers systemic drug levels and reduces the potential for harmful side effects. Many materials have been developed for drug delivery systems including liposomes, biodegraded polymer spheres, metal oxides, and other inorganic particles. Another advanced technology in the medical field is imaging with X-ray or magnetic contrast reagents.
Since chemotherapeutic agents have a reduced efficacy in non-proliferating cells, immunotherapy represents a valuable treatment option because it is able to eliminate tumor cells independent of their proliferative state. Tumor associated antigens have been identified for many tumors and those can serve as target for the immune system. One of the approaches used to induce immune responses against cancer cells are DNA vaccines. Injection of plasmids encoding polypeptides can induce immune responses against the transgene product, offering a potential means for immunization without requiring production and purification of complex antigens. Dendritic cells (DCs) are required to initiate the immune response to the transgene antigen(s) encoded by such DNA vaccines and cytotoxic T lymphocytes (CTLs) play a major role in eliminating malignant cells by specifically recognizing antigenic peptides presented on MHC class I molecules by dendritic cells (DC). DNA vaccines although showing some success, are not very efficient and new approaches are needed to improve efficacy.